1. Field of the Invention
The present invention relates to a high frequency module, and particularly relates to technology that can be effectively applied to a high frequency module including an antenna switch to be mounted on a mobile communication device or the like.
2. Background
In recent years, a mobile phone system is adopting various types of communication systems such as the GSM (Global System for Mobile Communications) (registered trademark) system and the W-CDMA (Wideband Code Division Multiple Access) system for realizing a variety of services.
Moreover, the frequency bands used in the respective systems are also diverse, and, for example, with the GSM system, an 850 MHz band, a 900 MHz band, a 1800 MHz band, a 1900 MHz band and the like are used. Moreover, with the W-CDMA system, an 800 MHz band, a 900 MHz band, a 1500 MHz band, a 1700 MHz band, a 1900 MHz band, a 2100 MHz band and the like are used.
In order to use a mobile phone in all countries of the world, a portable terminal that is compatible with a plurality of frequency bands and a plurality of systems is used, and the trend is to use a so-called multi-mode multi-band terminal.
With this type of mobile phone, a high-performance antenna switch capable of switching a plurality of frequency signals is used, and such an antenna switch is undergoing high functionality through, for example, SP4T (Single pole 4 throw) and SP6T (Single pole 6 throw) pursuant to the adoption of multi-band modes and multi-modes.
Moreover, since the CDMA system is compatible with high-speed data communication and the like, the antenna switch is demanded of high IMD (InterModulation Distortion) characteristics (low distortion) in a broad bandwidth.
As technologies for improving the IMD characteristics in this type of antenna switch, there are, for example, a type in which a voltage conversion circuit is activated and applies an output voltage to the antenna switch when the transmission power value of the transmission signal is greater than or equal to a threshold in order to improve the intermodulation distortion of the antenna switch (refer to Patent Document 1), a type which adopts a configuration of interposing in series an individual switch circuit and a common external terminal selector switch circuit in the paths between the common external terminal and the respective input/output terminal groups provided for each frequency band (refer to Patent Document 2), among others.    Patent Document 1: Patent Publication JP-A-2006-50590    Patent Document 2: Patent Publication JP-A-2009-165077
However, a number of problems exist in these methods and apparatuses.
During communication using the GSM system, the antenna switch is switched such that the antenna switch and the transmission terminal are connected during transmission and the antenna switch and the reception terminal are connected during reception, but with the W-CDMA system, the transmission and the reception are
Consequently, there is a problem in that the IMD characteristics of the antenna switch will deteriorate. IMD is a phenomenon that generates an output frequency component, which is a combination of the sum or difference of harmonics from reception signals of a frequency that differs from the transmission signals caused by the nonlinearity of the transistors configuring the antenna switch.
When a reception signal is received during transmission, an output frequency component is generated, which is a combination of the sum or difference of harmonics from reception signals of a frequency that differs from the transmission signals caused by the nonlinearity of the transistors configuring the antenna switch. As a result of this output, frequency component leaks to the receiver-side circuit via a duplexer or the like causing receiver sensitivity to deteriorate.